a. Field of the Invention
Broadly speaking, this invention relates to radar. More particularly, in a preferred embodiment, this invention relates to a Doppler radar system wherein the direction in which the target is travelling may readily be determined.
B. Discussion of the Prior Art
In many radar applications it is desirable to determine whether a particular target is approaching the antenna or receding from the antenna, that is, whether the target is "incoming" or "outgoing." It is also advantageous if the system can operate incoming targets from outgoing targets, as this ability may be used to yield a significant increase in the signal-to-noise and signal-to-clutter ratios of the system.
The fact that a target is moving may, of course, be determined by Doppler techniques, but to determine the sense of that movement, i.e., whether the target is incoming or outgoing, it is necessary to employ equipment yielding Doppler signals from quadrature RF channels.
In the prior art, such quadrature RF signals have required the use of separate RF demodulators in two, phase-matched RF channels. This makes the system expensive to manufacture and difficult to maintain. Further, if the sytem employs CW transmissions, the leakage between the transmitter and the RF demodulators will upset the phase-balance of the two channels.